1. Field of the Invention
The present invention generally relates m management of storage devices by a file server in a multimedia computer system and, more particularly, m an optimization scheme for load balancing/configuration planning in a video-on-demand computer system, sometimes called a movie-on-demand computer system.
2. Description of the Prior Art
Pay-for-view movies have been an increasingly popular service provided by cable TV operators and hotels for their subscribers and guests. The pay-for-view movies are typically stored on video cassette tape in analog form. The video cassettes may be loaded into a carousel which is programmed m play the movies at predetermined times. A subscriber or guest, having a set top converter, may select a movie, and that movie will be played at the subscriber's or guest's TV set at the programmed time. The subscriber or guest is automatically billed for the service.
This service, however, is not always convenient m subscribers and guests since movie selections are scheduled for certain time slots which may not fit a subscriber's or guest's schedule. More recently, movie-on-demand services are being provided which allow subscribers and guests to select a movie from a menu of available movies to be played on the subscriber or room TV at any time. This is made possible by storing the movies in digital form on magnetic disk and/or system random access memory (RAM). A movie stored on disk is first read into system memory and then read out as a data stream which is used to generate the analog TV signal that is supplied to a subscriber's or guest's TV set. If the movies which are played for a subscriber or guest are stored statically in system memory, read out can occur at any time without the limitations represented by the dynamic analog storage used in pay-for-view systems.
Movie-on-demand computer systems must be able to "play" multiple streams of many movies simultaneously. These movies may reside in memory or on one or more disks in the system. While a projection can be made as to the expected demand for any given movie currently available, the demand can vary widely. This in turn can cause a number of problems that will degrade the performance of the system. For example, perhaps the three most popular movies may be loaded from disk into system memory for play, but because of the limitations of system memory, the other movies available for play reside on disk. A portion of system memory is reserved to "page" in movies from disk as the movies are requested by subscribers and guests. Multiple copies of the more popular movies reside on multiple disks, although the number of copies will vary depending on the current popularity of the movies. Without some way to balance the load or demand on the several disks in the system, more requests to read a movie from a given disk may be made than can be serviced, with the inevitable result that service to subscribers and guests is degraded or even interrupted. This is an unacceptable situation, particularly where the subscribers and guests are paying a premium fee for the service.